Evolution of the semiconductor manufacturing industry is placing greater demands on yield management and, in particular, on metrology and inspection systems. Critical dimensions continue to shrink, yet the industry needs to decrease time for achieving high-yield, high-value production. Minimizing the total time from detecting a yield problem to fixing it determines the return-on-investment for a semiconductor manufacturer.
Fabricating semiconductor devices, such as logic and memory devices, typically includes processing a semiconductor wafer using a large number of fabrication processes to form various features and multiple levels of the semiconductor devices. For example, lithography is a semiconductor fabrication process that involves transferring a pattern from a reticle to a photoresist arranged on a semiconductor wafer. Additional examples of semiconductor fabrication processes include, but are not limited to, chemical-mechanical polishing (CMP), etch, deposition, and ion implantation. Multiple semiconductor devices may be fabricated in an arrangement on a single semiconductor wafer that are separated into individual semiconductor devices.
Metrology processes are used at various steps during semiconductor manufacturing to monitor and control the process. Metrology processes are different than inspection processes in that, unlike inspection processes in which defects are detected on wafers, metrology processes are used to measure one or more characteristics of the wafers that cannot be determined using existing inspection tools. Metrology processes can be used to measure one or more characteristics of wafers such that the performance of a process can be determined from the one or more characteristics. For example, metrology processes can measure a dimension (e.g., line width, thickness, etc.) of features formed on the wafers during the process. In addition, if the one or more characteristics of the wafers are unacceptable (e.g., out of a predetermined range for the characteristic(s)), the measurements of the one or more characteristics of the wafers may be used to alter one or more parameters of the process such that additional wafers manufactured by the process have acceptable characteristic(s).
In the semiconductor industry, the term haze can be used to describe the micro-roughness of a wafer surface. This can be a useful parameter for both integrated circuit and wafer manufacturers. Background scatter caused by imperfections on the surface of the substrate, such as intrinsic substrate roughness and polishing damage, leads to haze. Haze has been shown to correlate to a broad array of process parameters, such as surface roughness, grain size, and process temperature.
Many metrology tools and other tools in the semiconductor industry include an ultraviolet (UV) channel and an additional second wavelength or dual wavelength (DW) channel with a longer wavelength to detect the embedded defects within the photo-resistors or multi-layered structure for memory. For example, a longer wavelength of 488 nm may be used. There is no effective way to suppress the haze with the UV channel. Therefore, new techniques and systems to suppress haze are needed.